It's so tough to see the last painting, I can't comment on it. The one you called off center is actually centered on the head, but the flotation device is slightly off. Sometimes that can create a new tension, so live with it for awhile and see if it works, especially if you continue to make them off-center!
I like this work a lot, and dare I say, a lot more than your original sort of anatomy posts. How you continue and work the series will I think become a great exhibition.